Polycarbonates stabilized by halohydrocarbon, halocarbon or silane groups

ABSTRACT

A carbonate resin having the phenolic hydrogen end atoms replaced by stress corrodant preventive groups which are halohydrocarbon groups, halocarbon groups or a silane groups or the hydrogen end atoms replaced by a capping group having fluorescent properties to provide ultraviolet light and stress corrosive protection.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to my copending application Ser. No. 6,754,filed Jan. 26, 1979 pending in group, entitled "IMPROVED PLASTIC SOLARPANEL STRUCTURE AND METHOD AND APPARATUS FOR MAKING THE SAME". Theentire disclosure of my copending application is hereby incoporated byreference and relied upon.

BACKGROUND OF THE INVENTION

Numerous previous investigators have described methods for chemicallypassivating thermoplastic resins and for protecting certainthermoplastic resins from ultraviolet attack by additives that absorbincident radiation. Rauhut U.S. Pat. No. 3,974,368, Aug. 10, 1976,describes passivating polyethylene surfaces using silanes, e.g.,dimethydichlorosilane and the like. Uhl U.S. Pat. No. 3,810,775, May 14,1974, describes a process for making water repellant fiberous materialsby applying a copolymer of ethylene and a vinyl halosilane or vinylalkoxy silane. Anyos and Moyer U.S. Pat. No. 3,423,483, Jan. 21, 1969,describes production of a fluorescent polymer using polybenzoxazoleunits.

A modern process particularly suitable and often employed for theproduction of thermoplastic aromatic polycarbonates consists of reactingphosgene with suitable bisphenols in an aqueous solution or suspensionof alkali or alkaline earth metal salts. The polycarbonates that areobtained are high molecular weight linear chains of repeating units "X"and "Y"; distributed more or less at random; ranging from high ratios of"x"/"y" to high ratios of "y"/"x" having end groups of [HO--] and##STR1## where "X" is ##STR2## and Y is ##STR3## all more fullydescribed in Wulff, Schnell, and Bottenbruch U.S. Pat. No. 3,422,065,Jan. 14, 1969, the entire disclosure of which is hereby incorporated byreference and relied upon.

The linear chain polycarbonate thus produced can be cross-linked in thepresence of oxygen or free radical forming catalysts such as dibenzylperoxide and dicumyl peroxide with the resultant cross-linked polymerbeing much more insoluble than the linear polymer to high temperaturesteam. A preferred bisphenol intermediate for the cross-linkedpolycarbonate is "Bisphenol Cy" 1,1-bis(4 hydroxyphenyl) cyclododecane,but the resulting cross-linked resin presents substantially moredifficult processing parameters than the linear polycarbonate.

Examination of the stepwise attack on linear polycarbonates by strongbases offers an alternative to cross-linking for purposes of producingstress corrosion resistance while retaining favorable processingcharacteristics. Strong bases, and to a lesser extent, water, attemperatures ranging from 140° F. to 200° F. produce stress corrosionresponses in linear polycarbonates. This response is enhanced by thepresence of residual or induced stress and is increased with increasingtemperature. Stress corrosion responses characterized by cracking,pitting, loss of ductility, and weight loss by mass fall out of exposedareas may be noted as attacks following stepwise polymer bond breakage.Chemical reactions first producing bond breakage are most likely thoseinvolving relatively energy-rich, vulnerable, end group sites on thelinear polymer chain. The compounds formed by reacting the energy-richunits with stress corrodant constituents are more voluminous than thereactant and create a stress field sufficient to cause macroscopicfractures. The corrosion velocity or rate of attack is a function of therate of supply of an environmental reactant, and the amount of energy orstress available. Corrodant diffusion rates, surface to volume effects,and crack opening by external forces thus play important roles indefining attack velocities.

The importance of the end group's chemical reactivity may be noticed bycomparing preparation of thermoplastic polycarbonates with thepreparation of a thermoplastic polysulfone. Polysulfone is prepared byreacting bisphenol A and 4,4-dichlorodiphenyl sulfone with potassiumhydroxide in dimethyl sulfoxide. The characterisitc polysulfone resin##STR4## offers no site of high unit energy and minimal potential forchemical reactions causing pressure generating increased volumeproducts. It is necessary to remove all but slight traces of waterbefore polymerization to prevent hydrolysis of the dihydric phenol salt,and subsequent formation of the monosodium salt of4-chloro-4-hydroxydiphenol sulfone. End groups of [HO--] are absent.

In this connection consider the most common polycarbonate polyesterresin.

Polycarbonate polyesters produced from bisphenol A are characterized byunits of: ##STR5##

Polycarbonate resins may be slowly produced by a non-catalyzedcondensation reaction between bisphenol A and phosgene. ##STR6## where nis the degree of polymerization.

This reaction may be greatly accelerated by basic catalysts. With basiccatalyst acceleration, the reaction is assumed to be: ##STR7## Where Mis typically Li, Na, or K, obtained from a salt solution in aqueousmedium or from salt or hydride dissolution in the fused bisphenol Aresin.

Traces of the metal organic bisphenol, the catalytic salt, the hydroxylend groups, and unreacted bisphenol in the polycarbonate resin may causestress corrosion through the following typical stress producingreactions. ##STR8##

Exceptionally high proton mobilities in certain phases such as icecompared to water are illustrative of proton transfer along the hydrogenbond. Protons released by reactions with polycarbonate constituents alsodiffuse, forming hydroxyl and hydronium stress producing radicals.##STR9##

Polycarbonate resins may also be produced by catalytic synthesis ofbisphenol A and carbon monoxide: ##STR10##

This reaction is promoted by first dissolving the bisphenol A in asuitable solvent such as tetrahydrofuran (THF) and then activating itwith hydrogen. Activated hydrogen is introduced to the bisphenol Athrough the high shear path of reactor 300 in FIG. 5 (described later)to produce the following activated intermediate: ##STR11##

The activated intermediate is then immediately reacted with carbonmonoxide to produce polycarbonate. ##STR12##

This linear molecule may be grown as large as desired in the form:##STR13##

SUMMARY OF THE INVENTION

It is an object of the present invention to produce aromaticpolycarbonate resins having strongly bonded end caps resulting inuniform unit site free energies of formation and resistance to chemicalattack.

It is a further object of this invention to produce aromaticpolycarbonate resins having strongly bonded fluorescent polymer unitsresulting in interaction with incident light to wave shift ultravioletradiation portions to visible and infrared radiation.

It is another object of this invention to produce within aromaticpolycarbonate resins uniform unit site free energies of formation andinclude fluorescent polymer units during initial polymerization steps.

It is an additional object of this invention to react aromaticpolycarbonate resins with halogenated organo compounds duringthermoplastic processing of the polycarbonate resin to produce more orless uniform free energy unit sites throughout the polycarbonate chainincluding end caps. This object is further defined as a cost effectivemeans for limiting the amount of reactant halogenated organosilane toonly the replacement requirement for labile protons occurring at themolecular chain ends.

Stress relief annealing may be useful in occasional conventionalpolycarbonate product instances but upon the application of mechanicalloads or thermal stress in the presence of a stress corrodant, productfailures may be expected. The linear polycarbonate can, however, bemodified by preferentially reacting hydrogen at the end units with asuitable halogenated intermediate such as1,1,1-trichloro-2,2,2-trifluoroethane according to the following type:##STR14##

In the formulae R is an alkyl, cycloalkyl, aryl, or alkoxy group orhalogen atoms, and n is an integer of from 0 to 4. Examples of alkylradicals represented by R above having from 1 to 10 carbon atoms,preferably from 1 to 5 carbon atoms, are methyl, ethyl, propyl,isopropyl, butyl, pentyl, hexyl, octyl, and decyl; aryl radicals such asphenyl, naphthyl, biphenyl, tolyl, xylyl, and so forth; aralkyl radicalssuch as benzyl, ethylphenyl, and so forth; cycloalkyl radicals such ascyclopentyl, cyclohexyl, and so forth; alkoxy radicals having from 1 to5 carbon atoms, preferably from 1 to 3 carbon atoms are methoxy, ethoxy,propoxy, butoxy, pentoxy, as well as monovalent hydrocarbon radicalscontaining inert substituents therein such as halogen atoms, e.g.,chlorine, bromine or fluorine may be employed. It will be understoodthat where more than one R is used, they may be alike or different.

In the formulae A can be cycloalkylene, alkylidene, cycloalkylidene, orsulfone, R₁ can be alkylene, alkyleneoxyalkylene,poly(alkyleneoxyalkylene) or arylene, n₁ is an integer of at least oneand n₂ is 0 or an integer of at least one. The total of n₁ and n₂ issuch that the polymer normally has a molecular weight of more than about10,000, usually at least about 20,000 and can be up to about 150,000 orhigher. When n₂ is arylene then n₁ can be 0. Preferably, however, thereare more n₁ units than n₂ units.

The polymers are prepared in conventional fashion by reacting phosgenewith the appropriate dihydroxy compound or mixture of dihydroxycompounds.

Examples of suitable dihydroxy compounds for preparing thepolycarbonates are bis(4-hydroxyphenyl)cyclododecane,1,1-di-(4-hydroxyphenyl)-ethane, 1,1-di-(4-hydroxyphenyl)-propane,1,1-di-(4-hydroxyphenyl)-butane,1,1-di-(4-hydroxyphenyl)-2-methyl-propane,1,1-di-(4-hydroxyphenyl)-heptane,1,1-di-(4-hydroxyphenyl)-1-phenylmethane,di-(4-hydroxyphenyl)-4-methylphenylmethane,di-(4-hydroxyphenyl)-4-ethylphenylmethane,di-(4-hydroxyphenyl)-4-isopropylphenyl-methane,di-(4-hydroxyphenyl)-4-butylphenyl-methane,di-(4-hydroxyphenyl)-benzylmethane,di-(4-hydroxyphenyl)-alpha-furylmethane,2,2-di-(4-hydroxyphenly)-octane, 2,2-di-(4-hydroxyphenyl)-nonane,di-(4-hydroxyphenyl)-1-alpha-furyl-ethane,1,1-di-(4-hydroxyphenyl)-cyclopentane,2,2-di-(4-hydroxyphenyl)-decahydronaphthalene,2,2-di-(4-hydroxy-3-cyclohexylphenyl)-propane,2,2-di-(4-hydroxy-5-isopropylphenyl)-butane,1,1-di-(4-hydroxy-3-methylphenyl)-cyclohexane,2,2-di-(4-hydroxy-3-butylphenyl)-propane,2,2-di-(4-hydroxy-3-phenylphenyl)-propane,2,2-di-(4-hydroxy-2-methylphenyl)-propane,1,1-di-(4-hydroxy-3-methyl-6-butylphenyl)-butane,1,1-di-(4-hydroxy-3-methyl-6-tert.-butylphenyl)-ethane,1,1-di-(4-hydroxy-3-methyl-6-tert.-butylphenyl)-propane,1,1-di-(4-hydroxy-3-methyl-6-tert.-butylphenyl)-butane,1,1-di-(4-hydroxy-3-methyl-6-tert.-butylphenyl)-isobutane,1,1-di-(4-hydroxy-3-methyl-6tert.-butylphenyl)-heptane,1,1-di-(4-hydroxy-3-methyl-6-tert.-butylphenyl)-1-phenylmethane,1,1-di-(4-hydroxy-3-methyl-6-tert.-butylphenyl)-2-methyl-2-pentane,1,1-di-(4-hydroxy-3-methyl-6-tert.-butylphenyl)-2-ethyl-2-hexane,1,1-di-(4-hydroxy-3-methyl-6 -tert.-amylphenyl)-butane,di-(4-hydroxyphenyl)-methane, 2,2-di-(4-hydroxyphenyl)-propane,1,1-di-(4-hydroxyphenyl)-cyclohexane,1,1-di-(4-hydroxy-3-methylphenyl)-cyclohexane,1,1-di-(2-hydroxy-4-methylphenyl)-butane,2,2-di-(2-hydroxy-4-tert.-butylphenyl)-propane,1,1-di-(4-hydroxyphenyl)-1-phenylethane,2,2-di-(4-hydroxyphenyl)-butane, 2,2-di-(4-hydroxyphenyl)-pentane,3,3-di-(4-hydroxyphenyl)-pentane, 2,2-di-(4-hydroxyphenyl)-hexane,3,3-di-(4-hydroxyphenyl)-hexane,2,2-di-(4-hydroxyphenyl)-4-methylpentane,2,2-di-(4-hydroxyphenyl)-heptane, 4,4-di-(4-hydroxyphenyl)-heptane,2,2-di-(4-hydroxyphenyl)-tridecane,2,2-di-(4-hydroxy-3-methylphenyl)-propane,2,2-di-(4-hydroxy-3-methyl-3'-isopropylphenyl)-butane,2,2-di-(3,5-dichloro-4-hydroxyphenyl)-propane,2,2-di-(3,5-dibromo-4-hydroxyphenyl)-propane,di-(3-chloro-4-hydroxyphenyl)-methane,di-(2-hydroxy-5-fluorophenyl)-methane,di-(4-hydroxy-phenyl)-phenylmethane,1,1-di-(4-hydroxyphenyl)-1-phenylethane, and the like.

Any suitable aliphatic dihydroxy compounds may be used such as forexample, ethylene glycol, diethylene glycol, triethylene glycol,polyethylene glycol, thioglycol, ethylene dithioglycol, 1,3-propanediol,1,3-butanediol, 1,4-butanediol, 1,3-(2-methyl)-propanediol,1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol and thelike.

Any suitable cycloaliphatic dihydroxy compounds may be used such as, forexample, 1,4-cyclohexane-diol, 1,2-cyclohexane-diol,2,2-(4,4'-dihydroxydicyclohexylene)-propane, and2,6-dihydroxy-decahydronaphthalene.

Examples of suitable aromatic dihydroxy compounds which may be employedare hydroquinone, resorcinol, pyrocatechol, 4,4'-dihydroxydiphenyl,1,6-dihydroxynaphthalene, 2,6-dihydroxynaphthanele,1,4-dihydroxynaphthalene, 1,5-dihydroxynaphthalene, dihydroxyanthracene,2,2'-dihydroxydinaphthyl-1,1'- and o, m, and p-hydroxybenzyl alcohol andthe like.

In addition, di-(monohydroxyaryl)-sulfones may be employed such as, forexample, di-(4-hydroxyphenyl)-sulfone, di-(2-hydroxyphenyl)-sulfone,di-(3-hydroxyphenyl)-sulfone, di-(4-hydroxy-2-methylphenyl)-sulfone,di-(4-hydroxy-3-methylphenyl)-sulfone,di-(2-hydroxy-4-methylphenyl)-sulfone,di-(4-hydroxy-2-ethylphenyl)-sulfone,di-(4-hydroxy-3-ethylphenyl)-sulfone,di-(4-hydroxy-2-tert.-butylphenyl)-sulfone,di-(4-hydroxy-3-tert.-butylphenyl)-sulfone,di-(2-hydroxy-1-naphthyl)-sulfone and the like.

The preferred polycarbonates are those made from either bisphenol Aalone or a mixture of bisphenol A and bisphenol Cy. When thepolycarbonates are made from a mixture of bisphenol Cy (or ringsubstituted bisphenol Cy) with bisphenol A (or other dihydric compound)the polycarbonate will have X repeating units from the bisphenol Cy andY repeating units from the other dihydric compound (e.g., bisphenol A)in which the ratio of the units X:Y can vary widely, e.g., the ratio X:Ycan vary from 5:95 to 95:5.

In addition to the phenolic hydroxy end groups, the polymer also canhave the end group ##STR15## where R₂ is alkyl up to 4 carbon atoms,e.g., methyl, ethyl, propyl or butyl, cycloalkyl up to 6 carbon atoms,e.g., cyclopentyl or cyclohexyl, phenyl, alkylphenyl, e.g., p-tolyl,o-tolyl, p-ethylhexyl or p-butylphenyl, cycloalkyl phenyl, e.g.,p-cyclohexylphenyl, phenylamino, etc.

Elimination of an end group hydrogen and capping the polycarbonate chainend with a hydrophobic unit exemplifies one goal of the invention.

The preferred method for eliminating the vulnerable end unit hydrogen inthe polycarbonate chain is to react dried polymer, produced as describedabove, e.g., in the manner described in the Wulff et al U.S. Pat. No.3,422,065, with suitable pressurized vapor such as halogenated organosilicon compounds during pelletizing extrusion operations. This reactionis facilitated by the high surface to volume ratio of the powder andflakes of the polycarbonate resin feed stock, the agitation and kneadingprovided by the action of the extruder feed screws, and by the elevatedtemperatures attendant the melt-in process. The preferred point ofvaporous reactant introduction (see FIG. 2) is near the melt plug of theextruder 100. Hydrogen chloride, HBr, or HF gas or other gas produced bythe reaction is preferably vented to a water aspirator 102 connected tothe upper portions of the reaction extruder at 104.

By choosing the intermediate chemical to have end capping andfluorescent functions, another goal of the invention may be realized.For instance, 0.5 to 1.0 weight percenttrichlorodiphenyltriphenodioxazine may be added to polycarbonate duringinitial polymerization for purposes of producing a chemically boundfluorescent unit through labile hydrogen displacement. The resulting6,13-dichloro-3,10-diphenodioxazine unit has good stability and servesto convert incident U.V. radiation into longer wave length visible andinfrared radiation. Other suitable fluorescent end caps includebenzoxazole: produced by labile hydrogen displacement bychlorobenzoxazole or chlorobenzoxazole silane.

The polymerization end cap addition of fluorescent units having aboutthe same energy of formation as other polycarbonate units providespermanent U.V. and stress corrosion protection to the altered resin.U.V. energy is converted to visible and infrared energy. Stresscorrosion is prevented because there are no energy-rich sites forchemical attack.

The vulnerable phenolic hydrogen on the polycarbonate can be reactedwith other appropriate halogenated intermediates, especially where thehalogens are fluorine, chlorine or bromine, as well as with silanes.Typical compounds are volatile halocarbons, halohydrocarbons,halosilanes, halohydrosilanes. There can also be employed silanes whichare devoid of halogen. Examples of suitable reaction intermediates ofthe types just described are set forth in Table 1.

                                      TABLE 1                                     __________________________________________________________________________    Reaction Intermediates                                                        Com-                                                                          pound                                                                         __________________________________________________________________________    11  methacryloxypropyltrimethoxysilane                                                              CH.sub.2C(CH.sub.3)COO(CH.sub.2).sub.3 Si(OCH.sub.3)                          .sub.3                                                  12  mercaptopropyltrimethoxysilane                                                                  HSCH.sub.2 CH.sub.2 CH.sub.2 Si(OCH.sub.3).sub.3        13  glycidoxypropyltrimethoxysilane                                                                  ##STR16##                                              14  aminopropyltriethoxysilane                                                                      H.sub.2 NCH.sub.2 CH.sub.2 CH.sub.2 Si(OC.sub.2                               H.sub.5).sub.3                                          36  carbon tetrachloride                                                                            CCl.sub.4                                               15  trichlorofluoromethane                                                                          CCl.sub.3 F                                             16  dichlorodifluoromethane                                                                         CCl.sub.2 F.sub.2                                       17  chlorotrifluoromethane                                                                          CClF.sub.3                                              18  bromotrifluoromethane                                                                           CBrF.sub.3                                              35  carbontetrafluoride                                                                             CF.sub.4                                                19  chloroform        CHCl.sub.3                                              20  dichlorofluoromethane                                                                           CHCl.sub.2 F.sub.2                                      21  chlorofluoromethane                                                                             CH.sub.2 ClF                                            22  methylene fluoride                                                                              CH.sub.2 F.sub.2                                        23  1,1,2,2-tetrachloro-1,2-difluoroethane                                                          CCl.sub.2 FCCl.sub.2 F                                  24  1,1,1,2-tetrachloro-2,2-difluoroethane                                                          CCl.sub.3 CClF.sub.2                                    25  1,1,2-trichloro-1,2,2-trifluoroethane                                                           CCl.sub.3 FCClF.sub.2                                   26  1,1,1-trichloro-2,2,2-trifluoroethane                                                           CCl.sub.3 CF.sub.3                                      27  1,2-dichlorohexafluorocyclobutane                                                               C.sub.4 Cl.sub.2 F.sub.6                                28  chloroheptafluorocyclobutane                                                                    C.sub.4 ClF.sub.7                                       29  octafluorocyclobutane                                                                           C.sub.4 F.sub.8                                         5   chloromethyldimethylchlorosilane                                                                ClCH.sub.2 (CH.sub.3).sub.2 SiCl                        1   trimethylchlorosilane                                                                           (CH.sub.3).sub.3 SiCl                                   3   trichloromethylsilane                                                                           CH.sub.3 SiCl.sub.3                                     2   silicon tetrafluoride                                                                           SiF.sub.4                                               30  silicon tetrachloride                                                                           SiCl.sub.4                                              31  hydrasilicontrifluoride                                                                         HSiF.sub.3                                              6   hydrasilicontrichloride                                                                         HSiCl.sub.3                                             32  disilicon -exafluoride                                                                          Si.sub.2 F.sub.6                                        33  disilicon hexachloride                                                                          Si.sub.2 Cl.sub.6                                       34  tetrasilicon decafluoride                                                                       Si.sub.4 F.sub.10                                       7   silicon fluorochlorodibromide                                                                   SiFClBr.sub.2                                           8   methyl trichlorosilane                                                                          (CH.sub.3)SiCl.sub.3                                    37  dimethyl dichlorosilane                                                                         (CH.sub.3).sub.2 SiCl.sub.2                             9   trimethyl bromosilane                                                                           (CH.sub.3).sub.3 SiBr                                   4   triethylchlorosilane                                                                            (CH.sub.2 H.sub.5)SiCl                                  10  hexaethyldisilane (C.sub.2 H.sub.5).sub.6 Si.sub.2                        38  fluoroform        CHF.sub.3                                               39  acryloxypropyltrimethoxysilane                                                                   ##STR17##                                              __________________________________________________________________________

                  TABLE 2                                                         ______________________________________                                        Com-                                                                          pound  Fluorescent Reaction Intermediates                                     ______________________________________                                        41     6,13-trichloro-3-10-diphenyl-triphenodioxazine                         40     fluorodichlorodiphenyltriphenodioxazine                                44     quinine chlorosulfate                                                  46     3-aminochlorophthalimide                                               45     n-nitrochlorodimethylaniline                                           43     aluminum chelate of 2,2'-dihydroxy-1,1'-azonaphthalene-                       4-sulfonic acid                                                        47     4-dimethylchloroanimo-4-nitrostilbene                                  48     Rhodamine B-chlorosilane                                               49     Magdela Red Chlorosilane                                               42     Zinc trimethylsulfide                                                  50     Zinc dialkyl dithiocarbamates                                          52     4-(4-Nitrophenylazo) chlorophenol                                      53     Zinc ethyl xanthate                                                    54     Zinc fluoromethylsilane                                                59     Zinc ethyldichloroformate                                              57     Zinc isopropyldichloroformate                                          56     Zinc phenyldichloroformate                                             58     Zinc 1; 4 cyclohexanediol bischloroformate                             65     Rhodamine 110                                                          66     Rhodamine 19 Perchlorate                                               67     Zinc Xanthene                                                          68     Silicon Xanthene                                                       70     Rhodamine 123                                                          72     1-Naphthoyl Chloride                                                   55     Zinc benzoyldichloride                                                 60     Zinc phenylchlorocarbonate                                             61     Rubrene chloride                                                       62     Sodium Fluorescein                                                     63     Rhodamine B                                                            64     Rhodamine B Perchlorate                                                ______________________________________                                    

It should be realized that Table 1 and Table 2 are illustrative only andthe reactive intermediates are not limited thereto.

The amount of fluid reactant for replacing the phenolic hydrogen is notcritical. There should be enough employed to remove all of the phenolichydrogen atoms to provide the hydrophobic end unit but an excess of thefluid reactant can be employed.

Referring for the moment to previous Equations 1 through 8, as has justbeen pointed out, upon reaching the desired molecular weight, thepolymerization is terminated by addition of an end cap intermediateselected from Table 1 or Table 2 to produce desired chemical andphysical properties.

This end capping reaction is typified as shown in Equation 9. ##STR18##

Polymer produced by the above set out technique may be separated fromthe solvent by evaporation whereupon a clear film of tough stresscorrosion resistant polycarbonate is cast. This film may be cast uponselected substrates to produce laminates or spray cast upon silicone orfluorocarbon trays, conveyers, or wheels that allow peeling or sheddingaway the dry film for chopping and thermoplastic processing into film,sheet, tube and profiles.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be understood best in connection with the drawingswherein:

FIG. 1 shows vertical plasticizing extruder for carrying out the processof the invention;

FIG. 2 shows the screw and barrel assembly of the extruder of FIG. 1;

FIG. 3 illustrates details of the vent and port of the extruder;

FIG. 4 is a diagrammatic illustration of a polycarbonate polymerizationunit;

FIG. 5 is a diagrammatic illustration of a system for polymerizingpolycarbonate;

FIG. 6 is a diagrammatic illustration of a system for producing carbonmonoxide; and

FIG. 7 is a diagrammatic illustration of a reactor used in the system ofFIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in FIG. 1, the polymer conversion objects of the invention maybe realized with the aid of a plasticizing extruder. In operation, feedpolycarbonate resin, usually in the form of powder granules, flakes, orpellets is loaded by a suitable means such as vacuum loader 4 intodrying hopper 5. Resin entered into hopper 5 is held in residence untildry. This is usually accomplished by circulation of 250° F. dessicantdried -60° F. dew point air for resin exposures of 2 to 4 hours. Resinis then continuously fed by a double lead extension (not shown) of screw106 that extends about 12" into the bottom zone of hopper 5. Resin atabout 250° F. entering the upper zone (ZONE 1) of the 31/2" 30/l L/Dextruder is controllably further heated to between 300° F. and 450° F.by suitable sources such as electric resistance band heaters,circulating hot oil heaters, or steam jacket heaters. A vaporousreactant such as any of those set forth in Table 1 are delivered undersuitable pressure from source container 108 to pressure regulator 110and through line 112 to extruder barrel 116 at entry port 114. Entryport 114 is suitably an annular ring 3/8" wide×1/4" deep machined intothe inside diameter or bore of the outer shell of extruder barrel 116 atabout 24" below the entry to barrel 116. This distributor port ring iscovered by barrel inner liner of wear-resistant material selectiontypically no more than 1/4" in thickness. Small diameter (preferably0.030" max.) holes spaced at 1/4" circumferential intervals in thewear-resistant inner liner tube thus communicate the vapors deliveredfrom 112 to the resin mass within the extruder.

The reactant vapors are delivered under sufficient pressure to flow intothe compressed but non-fused resin mass and travel in both axialdirections, toward the resin entry and toward the extruder output. Vaporentrainment into the resin mass is assured by the kneading action ofscrew 106. It is preferred to cause entering resins within the feedsection to be more tightly compressed that at the first transitionsection. This is accomplished by utilizing a double screw flight designwithin the feed section followed by a single screw flight design throughthe first transition and remaining screw sections. The entry zone forreactant vapors therefore, is preferably at a point below most tightlycompacted resin and above a resin fusion point. As shown, the extruderscrew flight depth is preferably gradually diminished through thetransition zone to a first meter zone. Melt fusion of the resin at thelower portion of the first meter zone is maintained by control of theheater band settings in the first meter zone in conjunction with thescrew rpm. Vapors entering barrel assembly 116 through port ring 114 areimmediately reacted with resin surfaces and continue to react as theresin and entrained vapors are recompressed and resin melting occurs.Venting of by-product vapors such as HCl, HBr, and other volatilesthrough vent ring 104 is preferably at a point where approximately 60%to 80% of the resin mass has fused. Vent 104 is preferably an annulargap 3/8" wide×14" deep machined in the inside diameter outer shell ofbarrel assembly 116 about 56" below the top of the barrel. This ring isfitted with a porous sintered particle type 310 stainless steel cylindertreated with polytetrafluoroethylene for the purpose of allowingnon-plugging venting of unreacted vapors and by-product vapors to asuitable disposal facility. Vaporous effluent from 104 is deliveredunder developed pressure or to a suitable pump 102. This pump may be awater seal vacuum pump such as a NASH 1/2 HP or a water aspirator ofcommon design. Hydrogen halide vapors and resulting acids produced bythe above-described reactions are then neutralized by suitable basessuch as sodium hydroxide or other low cost alkaline mediums in sump 120.

Plastic resin masses achieving 100% fusion in the first melting zonecontinue to be worked by the action of screw 106 and undergo thoroughhomogenization through second transition and second meter zones of theextruder before exiting as completely reacted, homogeneous, stresscorrosion and ultraviolet radiation resistant thermoplastic suitable forforming by dies into any desirable shape.

Preparation of stress corrosion resistant polymers may be more desirablefor some products than preparation of combined ultraviolet and stresscorrosion resistant polymers. Selection of reactants from Table 1 offersa wide variety of final properties in addition to improved stresscorrosion resistance. For instance, extruded sheet and film productsmade from Compound 11, 12, 13, 14 (Table 1) vapor reacted polycarbonatehas enhanced adhesion to printing inks without the need for conventionalprimers, corona discharge, or flame treatments. Hot melt resin productsmade from polycarbonate resin so treated develop improved adhesion toall polyesters and thus offer an important improvement to weld joiningtechniques.

By using Compounds 2, 15, 16, 17, 18, 20, 21, 22, 23, 24, 25, 26, 27,28, 29, 32 and 35 (Table 1), the resulting stress corrosion resistantpolycarbonate is particularly grease and water repellant and thus suitedfor food service, home furnishing, and similar applications requiringantisoiling and low adhesion qualities. Products may be injectionmolded, fabricated sheet-like forms, or made from fiberous embodimentsand retain desired antisoiling properties.

Somewhat more economical achievement of greatly improved stresscorrosion resistance and for some applications a desirable degree ofhydrophobicity follows treatment using Compounds 1, 3, 4, 5, 8, 9, 10and 37 (Table 1) reactant vapors.

The vapor reactants cited above for purposes of producing improvedstress corrosion and ultraviolet resins vary greatly in chemicalreactivity. This is particularly true with respect to the agitation;smearing, and kneading of the reactants at elevated temperatures asprovided by the extruder. Thus it has been found useful in some cases todilute the vapors with an inert carrier gas such as carbon dioxide,nitrogen, argon, or dry air for purposes of preventing explosive ratesof reaction during introduction to the barrel at entry pressuressufficient to overcome locally existant resin pressures.

For instance, a mixture of 2% to 5%, e.g., 3.5%, trimethylchlorosilanein 95% to 98%, e.g., 96.5%, nitrogen (by volume) at an entry pressure of5 to 7, e.g., 6, atmospheres at 114 and 10 to 20 atmospheres at 126provides complete conversion of conventional bisphenol A basedpolycarbonate to stress corrosion resistant resin in a Type 430 outertube, Type 431 hardened inner liner, Type 431 hardened and chrome platedscrew, 31/2" diameter 30/l L/D ratio extruder. Nitrogen, hydrogenchloride gas, and unreacted excess trimethylchlorosilane pass throughvent 104 to disposal or recovery sink 120.

FIG. 3 illustrates details of vent 104 and port 114. (Port 126 istypical to port 114.) Braze sealed 3/8" AN type tube fitting 172 issufficiently large enough for adding reactant vapors to 3/8" wide×1/4"deep annular ring 166. Forty-four radially oriented 0.028" diameterholes 174 provide communication of entering vapors to the barrel asshown.

Vent 104 utilizes a stainless screen mesh or porous sintered Type 310stainless steel ring 160 to pass fluid vapors and gases while filteringsolid resin particles and flakes. The screen structure 160 is preferably250×250 mesh, 1/2" wide, spiraled 4 to 6 layers and seam welded at eachend. A stiff bristled stainless steel brush 154 is attached to screw 106as shown. In operation, the wire mesh filter cylinder 160 is continuallywiped clean by helically formed brush 154 which is attached to andempowered by screw 106.

The present invention further includes the development of uniform unitsite free energies of formation in polycarbonate resins through thefacility of liquid phase reactions. For example bisphenol A feed stocks,e.g., bisphenol A, may be dissolved in a suitable solvent such asethylene chloride, methylene chloride, petrol, ligroin, cyclohexane,methylcyclohexane benzene, toluene, xylene, chloroform,carbontetrachloride, trichloroethylene, dichloroethylene, methylacetate, and ethyl acetate and reacted with phosgene to producepolycarbonate. This reaction may, for purposes of maintaining desiredreaction rates be developed in an aqueous atmosphere and controlled byvarious additions of catalysts and pH modifiers as is conventional inthe art. Replacement of non-uniform free energy of formation end unitsand labile hydrogen may be accomplished in the separated non-aqueousliquid phase by addition of reactants selected from Table 1.

As an illustration of the liquid phase reaction, a mixture including10.8 lbs. bisphenol A, 4.7 lbs. sodium hydroxide, 22.4 lbs. methylenechloride, and 62.1 lbs. distilled water is agitated to a slurrysuspension and slowly phosgenated with about 4.9 lbs. phosgene. About0.36 lbs. of 4% solution of triethylamine is then added and the slurryis agitated for about two hours or until the desired molecular weight isreached. Additional methylene chloride may be added to reduce theviscosity of the organic phase to facilitate washing with hydrochloricacid and then with deionized water until neutral.

Phosgenation accelerated by the sodium hydroxide basic aqueousatmosphere thus produces polycarbonate in solution in methylene chloridethe polycarbonate having the general formula: ##STR19##

This solution and any water present may be dried by any suitable meansor evaporated completely to produce dry, clear, polycarbonate film, andredissolved in dry methylene chloride.

The polycarbonate in solution in dry methylene chloride or othersuitable solvent, e.g., a 15 to 60% by weight solution in methylenechloride may be reacted with a compound from Table 1, e.g., 0.01 to 5%of the compound by weight of the polycarbonate resin, to produce stresscorrosion resistant polycarbonate as follows: ##STR20## The reaction cantake place at 30° F. to 200° F. with the compound of Table 1 in gaseousform.

Removal of the hydrogen chloride or other similar by-product may be byaqueous neutralization washing followed by evaporative redrying, orthrough evaporation of the methylene chloride and venting of the HClvapors during melting of the resulting resin.

Phosgenation and modification of high free energy unit sites may also becarried out without the aid of water slurry atmospheres. Bisphenol Adissolved in suitable dry solvents such a dimethyl sulfoxide (CH₃SOCH₃), methylene chloride (CH₂ Cl₂), or ethylene dichloride (C₂ H₄Cl₂), in sufficiently dilute concentration to control reaction rates andresulting viscosity increases corresponding to molecular weight growthupon phosgenation provides a suitable atmosphere for reacting the newlypolymerized polycarbonate with a Table 1 reactant selected forspecifically desired resulting properties. The condensation reaction maybe terminated upon desired molecular growth by addition of dry ammoniaor hydrogen gas followed by an end group reactant selected from Table 1.##STR21##

For example: ##STR22## The resulting polymer illustrated has uniformunit site free energies of formation and increased hydrophobicity at theend caps. Other properties as discussed above may be achievedcorresponding to the reactant selected from Table 1.

Preparation of the polymer for thermoplastic processing such asinjection molding or extrusion involves separation of the by-productsHCl and NaCl, and evaporative recovery of the solvent. NaCl precipitatemay be filtered or centrifugally separated. It is preferred to recoverthe HCl as a valuable by-product for sale.

One of the preferred mechanical embodiments for polymerizing thepolycarbonate unit to the desired molecular weight is illustrated inFIG. 4. A coniform Type 310 stainless steel helical spiral 200 is brazedto an inside Type 310 stainless steel conical form 202 and to an outsideType 310 stainless steel conical form 204. The resulting tubular path206 is a coniform spiral starting at 210 and ending at 208. Attached tothe inlet 210 is a suitable tube connection 212 to pump 214, andattached to the outlet is a suitable tube connection 216, to form acirculation loop as shown involving the conical spiral and pump 214.

Selected solvent, e.g., methyl chloride, 600 parts by weight, andbisphenol A 230 parts by weight, in solution is pumped into theaforesaid pump 214 circuit by pump 220 from reservoir 218. Upon fillingthe pump 214 circuit, valves 222 and 224 are closed. Upon establishmentof a steady state rate of circulation of the bisphenol A in solventsolution through the pump 214 circuit, 110 parts by weight of phosgene(COCl₂) is admitted through valves 228 and 226 into the spiral portionas shown. The reaction is carried out at 90° F.

The buoyant upward force developed by the reactant phosgene gas issomewhat countered by the fluid motion forces of the bisphenol solventsolution that flows countercurrent to the phosgene's upward spiral. Thisinsures high exposure of the phosgene to the bisphenol A solventsolution.

Control of the reaction rate is offered by the rate of phosgeneaddition, the rate of circulation, and the reaction temperature. Optimumreaction temperature is maintained by heat exchange through pump circuit240 which is connected to a similar subspiral 242 constructed as 206 butpreferably circulated with hot or cold water.

Upon completion of the reaction and development of the desired molecularweight, e.g., after six hours, the polymerization is terminated byaddition of pressurized hydrogen through valves 226 and 230. Theinventory of solvent, and polycarbonate with hydrogen end groups is nowtransferred to reservoir 250. Replacement of fluids drained to 250 is byan inert gas such as argon, CO₂, or the like, as supplied from pressurecylinder 252 through valve 254 to accumulator 256.

Fluid stored in 250 may then be centrifugally filtered to remove NaClprecipitate and recirculated through a similar loop as described aboveto replace the hydrogen end caps with more desirable units as previouslydescribed by reaction with chemicals selected from Table 1, e.g., usingtrimethylchlorosilane at a temperature of 90° F.

Referring to FIG. 5, the system starts with unloading bisphenol A powderfrom railcar 330 through suitable line 332 to cyclone separator 324. 324is empowered by a suitable high-volume air pump 326. Dust is collectedin filter 328. Bulk storage of bisphenol A is provided in silo 322.Delivery through tube 332 to cyclone separator 319 and drier-hopper 320is empowered by pump 326 or a similar pump. Dissicant dryer 318 providesrapidly circulated -60° F. dew point, 250° F. air for an average dwelltime of two hours to dry powder in 320. Thoroughly dried, cleanbisphenol A is added through valve 321 to reservoir 308 where it isdissolved in a suitable solvent such as dimethylsulfoxide added throughvalve 309. The solution is passed through pump 306 and valve 304 toreactor 300. Reactor 300 is preferably constructed of 300 seriesstainless steel according to a design previously described with respectto reactor 204. Circulation of the dissolved bisphenol A and solvent isprovided by pump 356 through 3-way valves 353 and 354 to spiral path 302within reactor 300. Hydrogen is added through valve 340, pressureregulator 346 and valve 350 after being activated at 352. Activation ofhydrogen by heating and development of increased energy states uponpassage through an electrical arc in 352 decreases the requiredtemperature of the solution circulated through 300. Hydrogen is addeduntil the total pressure is about 250 psi. Variable displacement pump356 is operated so as to produce high shear flow of the bisphenol Asolvent solution through 300 as hydrogen is added. Valve 348 is thenclosed and carbon monoxide is admitted from 341 through valves 348 and350 to reactor 300. Hydrogen is released from the bisphenol A-hydrogenintermediate as carbonate radicals are formed and link bisphenol unitsinto polycarbonate polymer.

Displaced hydrogen is collected in separator 334 as the solution inreactor 300 is continually circulated until the desired molecular weightis reached. Hydrogen collected in separator 334 is then pumped bycompressor 336, through filter 338, valve 340, into storage as acompressed gas in 342. Upon reaching the desired molecular weight, thepolymer is end-capped by admitting a suitable reactant, selected fromTable 1 or Table 2 through valve 372 from reservoir 374. Polycarbonatepolymer of the desired molecular weight in solution is diverted throughvalve 353 to high pressure pump 358. Reactor 386, of a constructionsimilar to 300, may be employed to heat the polycarbonate-solventsolution under pressure to a temperature well in excess of theatmospheric pressure boiling point of the solvent. High pressuresolutions of polycarbonate and solvent are sprayed through suitablenozzles 360 on extended surface conveyor 362. Chamber 370 is operated attotal pressure below the partial pressure of the selected solvent andimmediate evaporation of the solvent is achieved. Solvent vapors arecondensed in condenser 314. Condensed liquid solvent is stored inreservoir 312. Polycarbonate which is deposited on conveyor 362 isdisplaced by rotary brooms 364 and 366. Flakes of polycarbonate arepelletized for handling, shipping, and further use efficiencies byextruder 392.

Bisphenol A resin in granular powder form is handled by conventionalchemical plant equipment including a suitable silo 322, hopper dryer320, dissicant type air drier 318 and mixer 308. The selected solvent iscondensed and handled by conventional chemical plant equipment,including a properly selected condenser tower 316, tank 312, valve 309,and mixer 308.

Bisphenol A dissolved in the selected solvent, e.g., methylene chloride,is circulated through conventional pump 306 and valve 304 to rector 300.Reactor 300 may be of any suitable conventional design but is preferablybuilt for purposes of producing extremely high surface to volume ratioflows of fluids and balancing high buoyant forces of reactant gasadditions with viscous forces of countercurrent flowing liquid fluids.In large-scale production, it is believed that a stainless steel,aluminum, or titanium alloy tube coil surrounded with a suitabletemperature control bath would produce an economical reaction path. Forinstance, a 600-foot long, Type 316, one-inch diameter stainless steeltube housed within a 600-foot long 11/4" diameter Type 316 stainlesssteel coaxial tube coiled on a vertical axis cylindrical or conicalsupport and fitted at each end with conventional Type 316 stainlesssteel coaxial braze fittings enables close temperature control fromfluid such as water or silicone fluid circulated in the O.D. tube.Circulation and conversion of more than 14,000 gallons of bisphenolA-solvent solution (e.g., using methylene chloride as the solvent) to14,000 gallons of polycarbonate-solvent solution per day may bepractically achieved. This enables about 600,000 pounds of low-cost,improved stress corrosion resistant polycarbonate per year to beproduced by the subject invention.

Polymerization of the polycarbonate to desired molecular weightsfollowed by end-capping and spray drying in 370 may also be accomplishedat considerable savings compared to conventional plant equipment.Pressurization by pump 358 of the heated polycarbonate-solvent solutionto 20 atmospheres pressure enables extremely fine sprays to be developedin airless spray nozzles 360.

Polymerized polycarbonate-solvent solutions sprayed from 360 may beaimed away from, parallel to, or at moving conveyor 362. Preferably thebelting of this conveyor is comprised of fluorocarbon materialmanufactured as a coarse plush, velvet-like rug, similar to someartificial turf materials. Extremely high surface areas expose dryingpolycarbonate films that are formed on the surface of the fluorocarbonvelvet hairs.

Dried polycarbonate films are to a large extent deposited on the outertips of the conveyor material. Upon reaching rotary broom 364, thesedeposits are whisked off of the conveyor surfaces and fall into thehopper around extruder screw extension 390. Rotary broom 364 is operatedat considerably higher tangential velocities than the conveyor surface.Another rotary broom 366 preferably operating at tangential velocitiesabove that of the conveyor provides pick-up and cleaning of surfaceslaid down by the action of 364. The continuous conveyor is then routedas shown, back to the spray line for facilitating the separation ofpolycarbonate and solvent.

Extruder 392 consists of a vented barrel 393, a screw 390, a gearreduction unit 396, and a drive motor 398. For the plant schematicallyillustrated in FIG. 5, the components are sized as shown in Table 2.

                                      TABLE 2                                     __________________________________________________________________________    Pilot Plant Example                                                           Component                                                                           Component                                                               Number                                                                              Name       Capacity    Specification                                    __________________________________________________________________________    332   Transfer tube                                                                            21/2 dia.   Aluminum tubing,                                                              polybutylene sweeps                              324   Cyclone separator                                                                        1,500 lb/hr Epoxy coat interior                                                           surfaces                                         326-328                                                                             Bag filter assy                                                                          100 lb/hr   Recyclable bag type                              322   Storage silo                                                                             200,000 lb. Welded construction,                                                          epoxy lined                                      320   Dryer hopper                                                                             1,000 lb.   Insulated for 360° F.                                                  service                                          318   Dissicant  1,500 GPM   -60° F. dew point;                                                     250° air                                  324   Solvent condenser                                                                        80,000 lb/day                                                                             Stainless steel                                  312   Holding tank                                                                             1,500 gal.  Stainless steel                                  308   Mixing tank                                                                              1,500 gal.  25HP totally                                                                  enclosed motor drive,                                                         stainless steel                                  306   Transfer pump                                                                            200 GPM, 10 PSIG                                                                          Stainless wetted                                                              components                                       304-309-                                                                            Flow control valves                                                                      200 GPM,    Stainless wetted                                 353-354-         3,000 PSIG  components solenoid                              359                          operated                                         336   Hydrogen compressor                                                                      3,000 PSIG, 10 HP totally                                                     3 stage     enclosed                                         342   Hydrogen storage                                                                         3,000 PSIG  Stainless steel                                  341   Carbon monoxide                                                                          3,000 lb/day                                                                              Incomplete combustion                                  production & storage   of carbon with oxygen                            340-349-                                                                            Gas control valves                                                                       3,000 PSI   Stainless steel                                  350                                                                           335-333-         1,000 GPM   solenoid operated                                372                                                                           346   Pressure regulator                                                                       0-300 PSI   Rated for CO, H.sub.2 with                                        1,000 GPM   downstream check valve                           334   Hydrogen separator                                                                       500 PSI,                                                           tanks      1,000 GPM                                                    300   Reactor    100 GPM, 500 PSI                                                                          Coaxial 1" bore and                                               400° F.                                                                            11/2" bore stainless                                                          steel tubes; 600' long                           388   Heat exchanger                                                                           100 GPM     Coaxial 1" bore and                                               3,000 PSI,  11/2" bore stainless                                              500° F.                                                                            steel tubes; 300' long                           358   Solution pump                                                                            100 GPM,    Stainless wetted                                                  3,000 PSI,  components, carbon                                                500° and ceramic seals                                370   Hermetically sealed                                                                      6' × 75'                                                                            Stainless steel                                        spray hopper                                                                             conveyor with                                                                             liner, insulated for                                              totally enclosed                                                                          250° F. operation                                          20 HP variable                                                                speed motor drive                                            393   Pelletizer 4" dia. 30/1;                                                                             Variable speed drive                                              L/D vented                                                                    extruder, 100 HP                                             380   Fluid heater/cooler                                                                      50 GPM 5° F. to 500°  F.                                        silicone oil;                                                                 heater or cooler,                                                             50 PSI                                                       __________________________________________________________________________

Carbon monoxide is preferably produced at the site of use by excesscarbon to oxygen combustion in a fluidized bed of relatively purecarbon. FIG. 6 illustrates the preferred embodiment for carbon monoxideproduction. Carbon delivered by any suitable means, including railcar450 is conveyed to storage silo 468 by suitable transfer and grindingequipment including tubing 452, cyclone separator 454, hammer mill 460,cyclone separator 462, filter bag 464, and blower 466. Carbon particlesranging from dust to pea-sized nodules stored in 468 are transferred todrier hopper 478 and into fluidized column 496 by screw 484. Hardened4140 steel screw 482 is preferably designed with a compression ratio ofabout 3/1; a screw diameter of 3", and an L/D ratio of about 15 forpurposes of compacting the carbon particles moving through transferbarrel 482, to form a seal against the flow of carbon monoxide producedin reactor 496.

Carbon monoxide is produced in reactor 496 by the combustion of carbonwith oxygen that may be supplied from any economical source. The surfacereaction starts on porous silicon carbide cone 499 through which oxygenpasses and combines with carbon supplied from the fluidized bed to formcarbon monoxide. Cone 499 is housed in reaction box 498, detailed morefully in FIG. 7.

    11/2O.sub.2 +2C→CO+CO.sub.2

Start-up requires electrical resistance heating cone 499 to 1,500° F. ormore. Cone 499 is maintained between 1,800° F. and 0° F. by control ofthe rate of oxygen addition through regulation of the oxygen pressure byregulator 500. Little carbon dioxide is produced however, any carbondioxide present on the surface of 499 is reacted with orange-white hotcarbon in 496 to produce carbon monoxide.

    CO.sub.2 +C→2CO

The carbon monoxide production is exothermic and once started, continuesat rates dependent upon the oxygen pressure. Heat produced by thereaction is carried upward within insulated reactor 496 to preheatcarbon working down to the reaction cone. Reactor 496 has a bore of 12",a height of 15', and is lined with a 0.250 wall Type 310 stainless steeltube. Carbon monoxide at about 250° F. is filtered through sinteredstainless steel shot filter 490 and is supplied at about 500 psi tostorage 341 for polycarbonate manufacture.

As shown in FIG. 7, stainless steel tube 496 is preferably welded toadapter flange 516. Adapter flange 516 is a 1" thick Type 310 stainlessplate and provides transfer of the column load of 496 to insulativebricks 521. 516 also supports Type 304 stainless steel cup 523 which issealed against 516 by a copper gasket and 12 equally spaced 1/2--13TPIscrews 525. Cup 523 provides support for porcelain insulator 530.Insulator 530 electrically isolates heat resisting compression spring528 that thrusts porcelain adapter cup 526 and silicon carbideresistance element 512 upward into tapered hole 510 of cone 499 toassure good electrical contact through all temperatures of operation.Cooling coil 532 provides circulation of suitable cooling fluids such assilicone oil to limit the temperature of the cylindrical walls of cup523 to about 400° F. Considerable cooling is provided by the incomingoxygen, however, on start-up and shut-down conditions, 523 requiresadditional heat dissipation through 532.

Start-up is provided by establishing a low positive pressure of oxygenthrough 524, and applying alternating 25 V, 300 A current through thecircuit 544, 542, 522, 512, 499, 516 and 546. Resistor element 512presents the most thermally insulated, highest resistance portion of thecircuit and reaches 2400°-2800° F. and heats 499 to at least 1500° F. byconduction and radiation. After carbon monoxide production is detectedat 486, electrical resistance heating may be stopped. Gas tight sealing499 to 516 is provided by conductive graphite electrode tar 518.

Shut-down is simply accomplished by stopping the flow of oxygen through524. Ash forming impurities in the carbon selected for carbon monoxideproduction eventually build a slag over 518 and in long production runsmay be removed by hot tapping through removable plug 552.

Rebuilding is usually required by erosion of 499 and destructive scalingof the lower portion of 496, and involves torch cutting 496 at asatisfactory height and at 516; removal of slag and 499; replacement of512, 518, 499 and the removed length of 496. Heliarc weld sealing thereplacement length of 496, restacking and banding insulative bricks 520,completes the short rebuilding process. More complete rebuilding toreplace cup assembly 523 involves removal of insulative bricks 520 and521; cutting 596 at a satisfactory height; disconnecting 524, 534, 542and 544; and change-out of pieces needing replacement.

Carbon selected for carbon monoxide production may be of any suitabledescription ranging from low ash coal products to petroleum sourcedcarbon black. The following examples assume that the carbon and oxygenpurity specifications allow direct carbon monoxide production withoutadditional purification except for non-volatile ash-slag disposal.

Unless otherwise designated, all parts and percentages are by weight.

EXAMPLE A Extruder Converted Resin

Polycarbonate resin such as that available from Mobay ChemicalCorporation designated by the brand name "Merlon" or from the GeneralElectric Company designated "Lexan" is processed through an extrudermodified to include vapor input ports above the melt zone. Each vaporinput zone is provided with a separate pressure regulator and inwardflow of reactant vapor is adjusted to produce a completely end-cappedpolymer. Vaporous reaction products are vented through an evacuated exitport between the entry ports.

In a 31/2" vertical 30/1 L/D, extruder, the upper inport port is about14" from the screw top (about 2" below the feed section of the screw);the exhaust vent is about 26" below the screw top; and the lower inportport is about 56" below the screw top. The extruder is run at 90 rpm andproduces a throughput of about 620 pounds of converted polycarbonate perhour, at a flange pressure of about 3,100 psi. The upper temperaturecontrol zone of the extruder corresponding to the feed section of thescrew is maintained at 250° F. The first vent zone corresponding to thesection between the feed section and the exhaust vent is maintained at350° F. The second vent zone, corresponding to the section between theexhaust vent and the lower input port is maintained at 450° F. Theremaining zones below the lower input port are maintained at 500° to520° F. A pelletizing die assembly that incorporates filter screens anda final vent is maintained at 500° F.

An end-capping reagent such as trimethyl chlorosilane [(CH₃)₃ SiCl] isadded at the upper and lower input vents at a total rate of about 25 to30 pounds per hour on start-up. The rate of addition is then graduallyreduced over a period of about one hour until a water-clear extrudatehaving completely converted end-caps is produced. Completeness ofconversion is determined by the ability of a 3-mil film cast from amethylene chloride solution of the produced polymer to withstand 30minutes contact at 300° F. with the residue of a 15% ammoniumlaurylsulfate-water solution without stress corroding. The minimumaddition rate of trimethyl chlorosilane depends upon the rate ofnon-reactive escape and upon the polycarbonate feedstock molecularweight and ranges between about 5 pounds per hour and 12 pounds perhour.

EXAMPLE B Solvent Atmosphere Converted Resin

Polycarbonate pellets such as resin designated "Lexan" or "Merlon" bythe General Electric and Mobay companies are dissolved in methylenechloride solvent. About 100 parts of resin are dissolved in about 700parts of solvent using a Neptune E blender. The solution is maintainedat about 50° F. in a coaxial tube reactor described above. About 5 partsof trimethyl chlorosilane [(CH₃)₃ SiCl] are gradually introduced to thesolution circulated in the reactor. Circulation through the reactor ismaintained at an average velocity of about 40' per second with astainless steel centrifugal pump for about 30 minutes. The convertedpolymer in solvent solution is transferred to a second reactor andpressurized to 2,000 psi with a positive displacement Pesco A-200 pump.The temperature of the polymer-solvent solution in the second reactor isgradually increased by about 250° F. by countercurrent heat exchangefrom heated silicone fluid. The heated solution is then pressure sprayedthrough four carbide tipped spray nozzles aimed so the most divergentportion of the fan is to a 2" deep, 4' wide, 10' long tray of water.Most of the methylene chloride solvent evaporates before the spraydroplets fall on the water. The sprayed flakes of convertedpolycarbonate are washed on a stainless screen with additional water,dried by a Conair D-280 Drier and extruded by a 2" extruder to producepellets.

EXAMPLE C

Bisphenol A resin is dried by passing -60° F. dew point, 250° F. airthrough a hopper containing the resin for three hours. 230 parts driedbisphenol A resin is mixed in 1,000 parts dimethyl sulfoxide and enteredinto a coaxial tube reactor by a Pesco A-100 positive displacement pumpand circulated at 40' per second average velocity. Additional solvent isadded to completely fill the reactor volume. The solution is pressurizedto 100 psi by heating to about 220° F. in response to circulation ofheated silicone fluid through the annular space between the outer tubeand the inner tube of the reactor. Hydrogen is added until the totalpressure is about 250 psi. Thirty parts carbon monoxide produced byreacting carbon with oxygen in a fluidized column are added to thecirculating solution of bisphenol A and dimethyl sulfoxide at about 300psi. The temperature of the circulating solution is reduced by heatexchange to 200° F. silicone fluid to about 210° F. during CO additionto maintain 300 psi overall pressure. Circulation is continued for about15 minutes or until the desired molecular weight has been reached. Themolecular weight is then fixed and the end groups capped by adding about25 parts Rhodamine 123. The temperature is then increased by circulationof 300° F. silicone fluid through the annular space between the coaxialtubes of the reactor and the pressure is increased by the restrictedthermal expansion of the solvent-solute solution to about 2,000 psi.Polycarbonate flakes are produced by spraying the 2,000 psi solutionover a bath of 70° F. isopropanol. Solvent escapes from the atomizedspray as solidified polycarbonate falls into the isopropanol to becollected.

EXAMPLE D

230 units of dry bisphenol A are dissolved in 1000 units of dry methanolat 80° F. The solution is pumped into a Type 316 stainless steel coaxialtube reactor by a Pesco A-100 pump and circulated at about 40 feet persecond. The solution is heated and pressurized to about 255° F., 400 psiby circulation of heated silicone fluids in the annular space betweenthe inner tube and the outer tube. Three parts hydrogen are passedthrough an electrical arc activator and added to the circulatingsolution. 35 parts carbon monoxide at about 250° F., 500 psi are added.The solution is slowly cooled to 80° F. and added to 1000 unitsmethylene chloride. The double solvent solution is circulated withsamples taken every five minutes until a suitable molecular weight isreached. The molecular weight growth is terminated and end caps aredeveloped by adding 1.5 parts 3-amino chloroacridine. The polycarbonaterich methylene chloride solution is centrifugally separated from themethanol solution and polycarbonate is precipitated by any suitablemeans or deposited as a clear varnish upon evaporation of the methylenechloride solvent.

EXAMPLE E

100 units of dry polycarbonate are dissolved in 1200 units methylenechloride. 750 units dry methanol are added and a portion of the solutionis transferred to the inner tube of a 1000 ml stainless steel coaxialtube reactor packed with wheat grain size zinc shot. This portion isdesignated Sample "A". Silicone oil is circulated between the outer tubeand inner tube for temperature control. The solution in the inner tubeis circulated through the zinc shot with a hermetically sealed positivedisplacement pump. The circulating solution is brought to 250° F. and 15units of 1,1,2-trichloro-1,2,2-trifluoroethane are added. Circulation iscontinued for 10 minutes at 250° F. and then cooled to 70° F.

Polycarbonate from samples of the reacted solution (Sample A) and theunreacted solution (Sample B) are cast by evaporation. Sample A is foundto resist stress corrosion from 15% ammonium laurylsulfate solutionresidues at 300° F. while Sample B fails to resist stress corrosionunder the same test.

EXAMPLE F

100 parts of Lexan polycarbonate are dissolved in 700 parts methylenechloride at 70° F. A sample of solution is withdrawn and marked SampleA. 5 parts 1-naphthoyl chloride are added to the remaining solution andthe solution is stirred for 30 minutes. A second sample is withdrawn andmarked Sample B. Films are cast from Samples A and B. Comparison ofaccelerated ultraviolet testing of samples A and B show markeddifferences with Sample B showing reduced yellowing and embrittlementdue to ultraviolet exposure. A and B comparisons of stress corrosion dueto exposure to the residues of a 15% ammonium lauryl sulfate-watersolution at 300° F. show reduced effect upon Sample B.

Unless otherwise indicated all parts and units are by weight. Parts andunits are used interchangeably. The composition can comprise, consistessentially of or consist of the materials set forth. The process cancomprise, consist essentially of or consist of the steps set forth.

What is claimed is:
 1. A polycarbonate resin having the phenolichydrogen end atoms replaced by stress corrodant preventive groups whichare halohydrocarbon groups, halocarbon groups or a silane groups.
 2. Apolycarbonate resin according to claim 1 wherein the stress corrodantpreventive group is a halohydrocarbon group or a halocarbon group and atleast a portion of the halogen is fluorine.
 3. A polycarbonate resinaccording to claim 1 wherein the stress corrodant preventive group is asilane and is a lower alkyl silane, a halosilane, a haloalkylsilane, ahydrasiliconhalide, an amino lower alkyl lower alkoxy silane, aglycidoxy lower alkyl lower alkoxy silane, a mercapto lower alkyl loweralkoxy silane, an acryl or methacryl oxy lower alkyl lower alkoxysilane.
 4. A polycarbonate resin according to claim 3 having the formula##STR23## where A is cycloalkylene, alkylidene, cycloalkylidene, orsulfone, R₁ is alkylene, alkyleneoxyalkylene, poly(alkyleneoxyalkylene)or arylene, R is alkyl, cycloalkyl, aryl, aralkyl, alkoxy or halogen ofatomic weight 9 to 80, n is an integer from 0 to 4, n₁ is an integer ofat least one, n₂ is 0 or an integer of at least one, the total of n₁ andn₂ is such as to define the molecular weight of the polymer with theproviso that when n₂ is arylene then n₁ can be 0 and X is the stresscorrodant preventive group.
 5. A polycarbonate resin according to claim4 includes bisphenol A units as a part of the units in n₁.
 6. Apolycarbonate resin according to claim 5 wherein n₂ is
 0. 7. Apolycarbonare resin according to claim 6 wherein all the n₁ units arebisphenol A units.
 8. A polycarbonate resin according to claim 6 whereina portion of the n₁ units are bisphenol Cy units.
 9. A polymer accordingto claim 6 wherein X is ##STR24## where R₁, R₂ and R₃ are all loweralkyl.
 10. A polymer according to claim 9 wherein R₁, R₂ and R₃ are allmethyl.
 11. A process of preparing the polycarbonate resin of claim 3comprising extruding a polycarbonate resin having phenolic hydrogen endatoms and adding the silane to the resin in the extruder to form thesilane containing stress corrodant preventive groups in place of thehydrogen end atoms.
 12. A process according to claim 11 wherein thesilane is added in gaseous form.
 13. A process according to claim 11wherein the silane is trimethylchlorosilane.
 14. A process of preparingthe polycarbonate resin of claim 3 comprising adding a silane to asolution of a polycarbonate resin having phenolic hydrogen end atoms andallowing the silane to react with the polycarbonate resin in solutionuntil there are formed silane containing stress corrodant preventivegroups in place of the hydrogen atoms.
 15. A process according to claim14 wherein the silane is trimethylchlorosilane.
 16. A process accordingto claim 15 wherein the solvent is methylene chloride or dimethylsulfoxide.
 17. A process according to claim 14 wherein the silanereaction is accelerated by heating the polycarbonate solution.
 18. Aprocess of preparing the polycarbonate resin of claim 2 comprisingextruding a polycarbonate resin having phenolic hydrogen end atoms andadding the fluorine containing halohydrocarbon or halocarbon to theresin in the extruder to form the fluorine containing stress corrodantpreventive groups in place of the hydrogen end groups.
 19. A processaccording to claim 18 wherein the fluorine containing compound is addedin gaseous form.
 20. A process of preparing the polycarbonate resin ofclaim 2 comprising adding a fluorine containing halohydrocarbon orhalocarbon to a solution of a polycarbonate resin having phenolichydrogen atoms and allowing the fluorine containing compound to reactwith the polycarbonate resin in solution until there are formed fluorinecontaining stress corrodant preventive groups in place of the hydrogenend atoms.
 21. A process according to claim 20 including heating thesolution.
 22. A process according to claim 21 wherein the heating is to300° F.
 23. A process of preparing the polycarbonate resin of claim 1comprising extruding a polycarbonate resin having phenolic hydrogen endatoms and adding a silane, halohydrocarbon or halocarbon to the resin inthe extruder to form the stress corrodant preventive groups in place ofhydrogen end atoms.
 24. A process according to claim 23 wherein thesilane, halohydrocarbon or halocarbon is added in gaseous form.
 25. Aprocess of preparing the polycarbonate resin of claim 1 comprisingheating a solution of a polycarbonate resin having phenolic hydrogen endatoms, said solution also containing a silane, halohydrocarbon orhalocarbon, to a temperature sufficient to react said silane,halohydrocarbon or halocarbon with said resin and form stress corrodantpreventive silane, halohydrocarbon or halocarbon end groups in place ofthe hydrogen end atoms.
 26. A process according to claim 25 wherein theheating is to at least 300° F.
 27. A polycarbonate resin according toclaim 1 wherein the stress corrodant preventive group is ahalohydrocarbon group or a halocarbon group.
 28. A polycarbonate resinaccording to claim 27 wherein the halohydrocarbon or halocarbon groupcontains chlorine.
 29. A polycarbonate resin having the phenolichydrogen end atoms replaced by a capping group having fluorescentproperties to provide ultraviolet light and stress corrosion protection.30. A polycarbonate resin according to claim 29 wherein the cappinggroup contains a 6,13-dichloro-3,10-diphenodioxazine unit or abenzoxazole unit
 31. A polycarbonate resin according to claim 29 whereinthe capping unit is formed by reacting the polycarbonate withtrichlorodiphenyltriphenodioxazine, chlorobenzoxazole orchlorobenzoxazole silane.
 32. A polycarbonate according to claim 31wherein the capping unit is formed by reacting the polycarbonate withtrichlorodiphenyltriphenodioxazine.
 33. A polycarbonate according toclaim 31 wherein the capping unit is formed by reacting thepolycarbonate with chlorobenzoxazole.
 34. A polycarbonate according toclaim 29 containing capping units of both (1) a compound impartingfluorescent properties to the polycarbonate and (2) a halohydrocarbon, ahalocarbon or a silane.
 35. A polycarbonate according to claim 34wherein (2) is a silane.
 36. A polycarbonate according to claim 35wherein the capping units are formed by reacting a polycarbonate withboth (1) trichlorodiphenyltriphenodioxazine or chlorobenzoxazole and (2)a silane.
 37. A polycarbonate according to claim 36 wherein the silaneis trimethylchlorosilane.
 38. A polycarbonate resin according to claim 1wherein the halohydrocarbon or halocarbon group contains chlorine and isthe residue from removing one of the atoms attached to the carbon atomof methylene chloride, chloroform or carbon tetrachloride.